pnmscale(1)

pnmscale is part of the Netpbm package. Netpbm documentation is kept in HTML format. Please refer to <http://netpbm.sourceforge.net/doc//pnmscale.html>. If that doesn't work, also try <http://netpbm.sourceforge.net> and emailing Bryan Henderson, bryanh@giraffe-data.com.